The fixed bed sweetening of hydrocarbons is well known in the art. For example, a typical process is disclosed in U.S. Pat. No. 2,988,500, wherein a sour petroleum distillate is contacted with a fixed bed of a metal phthalocyanine catalyst combined with a charcoal carrier in the presence of oxygen and an alkaline reagent. In fixed bed treating processes in general, the refiner has a high degree of control over the sweetening operation, and can be reasonably sure that all of the hydrocarbon passing through the fixed bed will be treated.
Liquid-liquid sweetening is also well known in the refining arts. In this process a metal chelate is dispersed or dissolved in an alkaline medium. The alkaline medium can be used to extract mercaptans from a hydrocarbon stream, with regeneration of the alkaline medium via oxidation of mercaptans to disulfides occurring in a separate vessel. Alternatively, the hydrocarbon, the alkaline medium with catalyst, and an oxidizing agent may be contacted in a single vessel. An example of this is provided by U.S. Pat. No. 3,853,432, which discloses many details of catalysts and alkaline mediums which may be used. That patent also teaches that it is desirable to use a sulfonated derivative of a metal phthalocyanine to increase the solubility of the phthalocyanine catalyst in the alkaline medium.
A feature common to these and other sweetening operations is use of a metal phthalocyanine catalyst. Many methods of metal phthalocyanine preparation are known in the art. One such method involves contacting metal hydroxide with quinoline in an inert organic solvent and subsequently adding a solution containing a phthalonitrile to obtain the desired phthalocyanine compound. The metal phthalocyanines may be halogenated by various procedures, such as are shown in U.S. Pat. Nos. 3,393,200 and 3,252,992. Further, U.S. Pat. No. 3,074,958 discloses a method for the preparation of a metal phthalocyanine compound by heating a mixture containing a phthalic acid, urea or another nitrogen donor, a metal donor and ammonium chloride, which improves the yield of the metal phthalocyanine compound.
However, some of the phthalocyanines produced by known processes suffer from insufficient solubility in the stream requiring sweetening, particularly in streams requiring reduction in mercaptan levels. This problem is encountered particularly in liquid-liquid processes, and has prompted work to be done towards preparing sulfur-containing derivatives of metal phthalocyanines. The solubility problem has also been addressed in another art, that of dyes and pigments, where metal phthalocyanines also find use.
There are known only a few methods of forming sulfur-containing derivatives of metal phthalocyanines. Perhaps the oldest method is sulfonation in oleum. One example of this sulfonation method is given in U.K. 503,029, which teaches a way to prepare copper phthalocyanines, followed by reaction of the phthalocyanines with sulfuric acid to produce a product termed a sulphate. Preparation of tetra-sulfo copper-phthalocyanines is disclosed in Sekiguchi, et al., Chem. Abstracts, Volume 71, Item 1031530 (1969), wherein a tetrasulfonate is made by first preparing the phthalocyanine and then sulfonating in oleum or sulfuric acid.
Day, in J. Chem. Soc. (A), 90 (1963), disclosed preparing a cobalt phthalocyanine tetrasulfonate from cobalt phthalocyanine by sulfonation in sulfuric acid and oleum. Borisenkova, et al., ZH. Organischeskoi Khim., 9, 1822-1830 (1973), also disclosed preparation of phthalocyanines by the reaction of metal powder with phthalonitrile. The phthalocyanines were prepared using nitrobenzene as a solvent. This material was sulfonated using oleum.
A second category or type of preparation of sulfur-containing derivatives of phthalocyanine involves preparing a phthalocyanine from reactants already containing a sulfur moiety. In these methods any phthalocyanine prepared is automatically a sulfur-containing phthalocyanine. One of these is disclosed by Fukada, in Nippon Kagoku Zasshi 79, 396-0 (1958), which shows various methods of preparation of phthalocyanine tetrasulfonates. Fukada prepares his tetrasulfonate using triammonium 4-sulfophthalate, by carrying out a reaction at 240° C. Various modification of Fukada's method have been proposed, including Webber and Busch's modification disclosed in Inorg. Chem. 4, 469-71 (1965), ibid., 472-5, wherein nitrobenzene is used as a solvent. Another variation is disclosed by Kundo et al., Kinet Katal 8, 1325-30 (1967), which teaches a melt, or dry, reaction which occurs at 200 to 210° C. for six hours. Kundo et al. disclose that their catalyst can convert cysteine to cystine. This is an example of conversion of a mercaptan to a disulfide, though Kundo uses a biological system involving an amino acid.
Another closely related method of preparing sulfur-containing phthalocyanines is disclosed by Przywarska-Boniecka, Rocz. Chem. 41, 1703-10 (1967), which includes a method similar to Fukada's, but mentions that the maximum reaction temperature should be 240° C. The metal used in that study is rhenium. Oxidation of mercaptans was not studied.
In general, there exists one or more drawbacks of known treatment compositions that include sulfonated iron-phthalocyanine. One drawback is that the sulfonated iron-phthalocyanine reaction products tend to have an undesirable impurity load. Such impurity loads can cause manufacturing and/or use issues. For example, in the context of including sulfonated iron-phthalocyanine in a treatment composition to treat a hydrocarbon, such treatment compositions may exhibit one or more of the following undesirable characteristics during one or more hydrocarbon treatment processes: poor filtering, excessive foaming of the treatment composition, contamination of the treatment composition, and iron solids. Another drawback is that many methods of making sulfonated iron-phthalocyanine are known to result in residual promoter being present in the reaction product. Although tolerable when these materials are used as dyes, residual promoter can undesirably hinder the complexing activity of a sulfonated iron-phthalocyanine in the context of hydrocarbon treatment. Yet another drawback can be poor stability/vulnerability of a sulfonated iron-phthalocyanine to oxygen in the ambient or oxygen that may be dissolved in admixture containing the phthalocyanine material. Exposing sulfonated iron-phthalocyanine to oxygen can undesirably cause Fe(II) to convert to Fe(III) which is vulnerable to iron-sulfide/iron-hydroxide solids formation. This vulnerability to oxygen makes the sulfonated iron-phthalocyanine difficult to use in practice.